Gyraulus sp.
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publication ID |
https://doi.org/ 10.4202/app.00469.2018 |
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publication LSID |
lsid:zoobank.org:pub:153CB896-6EE8-48F1-A330-80FCD3B1ED94 |
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persistent identifier |
https://treatment.plazi.org/id/03C387DC-7817-9362-FF86-FDBB5476912A |
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treatment provided by |
Felipe |
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scientific name |
Gyraulus sp. |
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Fig. 5F–I View Fig .
Material.—Ten specimens: NHMW 2018 View Materials /0019/0025 ( Fig. 5F View Fig ) ; NHMW 2018 View Materials /0019/0026 ( Fig. 5G View Fig ) ; NHMW 2018 View Materials / 0019/0027 ( Fig. 5H View Fig ) ; NHMW 2018 View Materials /0019/0028 ( Fig. 5I View Fig ) ; NHMW 2018 View Materials /0019/0028a (6 specimens) from the upper Susuz Formation ( upper Oligocene or lower Miocene ) at Kömürlü, Oltu-Narman Basin, northeastern Turkey .
Description.—Small, glossy, planispiral, rather evolute shell ( Table 6) comprising three whorls with moderately incised suture. Protoconch poorly preserved in all specimens. Lower and upper sides slightly concave; umbilicus and spire only weakly sunken; teleoconch whorls on lower side weakly convex in middle part of whorls, passing into nearly straight part towards periphery. Whorls flattened on upper side resulting in rather flat profile. Periphery coinciding with marked central angulation without forming keel. Distinct, prosocyrt growth lines on lower side but nearly smooth on upper side. Last whorl slightly bent towards upper side in some specimens. Aperture heart-shaped, wider than high, weakly inclined.
Remarks.—The specimens resemble several species of the European Oligocene to early Miocene. Planorbis? amblytropis Sandberger, 1871 , from the Chattian of Vicques Recolaine), Switzerland, and Gyraulus goussardianus Noulet, 1854 ) (sensu Fischer 2000), from the late early to early middle Miocene of Sansan, France, both share with the present specimens the marked central angulation, the whorl expansion rate, the flat profile and the strong growth lines; only the aperture seems to be wider in both species. Similarly, Gyraulus douvillei ( Saporta, 1889) , from the Chattian of southern France, resembles the present specimens in terms of whorl expansion rate, growth line strength and the presence of a keel. Unfortunately, Saporta (1889) did not specify the exact location of the keel and did not provide an illustration of the shell profile. The studied specimens might be conspecific with one of these species, but the rather poor preservation of the present material, as well as the insufficient knowledge of the tentative European relatives, complicates reliable determination.
Other angulated or keeled forms comprise Gyraulus ludovici ( Noulet, 1854) from Sansan, which differs in the apical angulation and the low whorl expansion rate, and Gyraulus applanatus ( Thomä, 1845) , from the early Miocene of the Mainz Basin ( Germany), having its keel near the base. Early Miocene Gyraulus dealbatus (Braun in Walchner, 1851) differs in the only weak, subcentral angulation and the lower whorl expansion rate (see also Harzhauser et al. 2014b).
A relation with genus Hippeutis Charpentier, 1837 is unlikely. Species attributed to that genus are characterized by flatter shells with marked keel and often concave margins (e.g., Welter-Schultes 2012; Harzhauser et al. 2014b).
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